传感光纤-砂土界面力学性质的试验研究

EXPERIMENT STUDY ON MECHANICAL PROPERTIES OF INTERFACE BETWEEN SENSING OPTICAL FIBER AND SAND

近年来分布式光纤感测技术在岩土与地质工程领域的应用研究已成为一个研究热点,但工程实践表明,埋入式传感光纤与被测岩土体之间的变形协调性会对监测结果产生显著的影响,该问题一直制约着光纤感测技术在工程监测中的推广。本文通过一系列室内拉拔试验,对比了3种预埋于砂土中的单模光纤在不同上覆压力的作用下的拉拔力-拉拔位移曲线,并建立了一个用于描述光纤-砂土界面力学性质的三段式的拉拔模型,分析峰值拉拔力、残余拉拔力、有效拉拔位移和残余拉拔位移4个参数在不同上覆压力作用下的变化情况。分析结果揭示传感光纤-砂土界面的力学特性和应力传递规律,为分布式光纤传感技术在岩土体变形监测中的应用,尤其在变形监测光纤的选用标准方面,提供了参考依据。

In recent years,the application of distributed optical fiber sensing (DOFS )technologies to geo-engineering monitoring has been a research focus.But in engineering practices,the deformation compatibility between the embedded sensing optical fibers and the soil and rock masses can significantly affect the monitoring results,which is the main barrier for the DFOS based engineering monitoring.This paper is based on a series of laboratory pullout tests on the three types of the single-mode optical fibers embedded in sand.The comparisons between the pullout force-pullout displacement curves of these fibers under different overburden pressures are conducted.A tri-linear pullout model is established to describe the fiber-sand interfacial mechanical characteristics. Using this model,the variations of the four model parameters,i.e.peak pullout force,residual pullout force, effective pullout displacement and residual pullout displacement, are analyzed considering the influence of overburden pressure.The analysis results indicate the mechanical properties of fiber-sand interface and stress-transfer mechanism,which provides valuable references for the application of the distributed optical fiber optic sensing to soil deformation monitoring,especially in terms of selection criterion of the deformation sensing fiber.